Enhanced photoelectrochemistry and interactions in cadmium selenide–functionalized multiwalled carbon nanotube composite films

Cadmium selenide–functionalized multiwalled carbon nanotube (CdSe–f-MWCNT) composite films have been synthesized by the percolation of a f-MWCNT dispersion through the macropores of electrodeposited CdSe thin films during electrophoretic deposition. Evidence for efficient charge transfer from CdSe to f-MWCNTs was obtained by photoluminescence quenching and proof for strong interactions was provided by X-ray photoelectron spectroscopy analyses, which revealed a significant decrease in the reduced Se2− content and evolution of new signals due to oxidized Se, and high resolution transmission electron microscopy and atomic force microscopy images of CdSe decorated f-MWCNTs in the composite film. Sputter depth profiling of the composite confirmed a homogeneous mixing of nanoparticulate CdSe and f-MWCNTs. A quasi solid-state photoelectrochemical cell fabricated by coupling the composite film with an ionic liquid based gel polymer electrolyte containing the I3/I− redox pair not only showed larger photocurrents, photovoltage and incident photon to current conversion efficiency as compared to the analogous CdSe cell but also showed a remarkably enhanced stability to photoerosion. The ability of f-MWCNTs to mediate fast charge transfer and retard charge recombination rate in the composite was also evident from electrochemical impedance spectroscopy (EIS) results. Cell degradation upon exposure was also reflected in the altered EIS parameters such as increased charge transfer resistance and the reduced ease of charge transport through the composite.